Convertible Senior Notes (Liability Component) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Debt Disclosure [Abstract]
Principal	$ 275,000,000		$ 275,000,000
Less: Debt discount, net	(36,317,000)	[1]	(38,912,000)	[1]
Net carrying amount	238,683,000		236,088,000
Fair value of Notes	$ 263,000,000
Remaining contractual life	3 years 2 months 1 day

[1] Included in the consolidated balance sheets within convertible senior notes (due 2017) and amortized to interest expense over the remaining life of the Notes using the effective interest rate method.